Effects of radiant exposure and wavelength spectrum of light-curing units on chemical and physical properties of resin cements

Lima, Adriano Fonseca,Formaggio, Stephanie Ellen Ferreira,Zambelli, Ligia Franca Aires,Palialol, Alan Rodrigo Muniz,Marchi, Giselle Maria,Saraceni, Cintia Helena Coury,de Oliveira, Marcelo Tavares The Korean Academy of Conservative Dentistry 2016 Restorative Dentistry & Endodontics Vol.41 No.4

Objectives: In this study, we evaluated the influence of different radiant exposures provided by single-peak and polywave light-curing units (LCUs) on the degree of conversion (DC) and the mechanical properties of resin cements. Materials and Methods: Six experimental groups were established for each cement (RelyX ARC, 3M ESPE; LuxaCore Dual, Ivoclar Vivadent; Variolink, DMG), according to the different radiant exposures (5, 10, and $20J/cm^2$) and two LCUs (single-peak and polywave). The specimens were made (7 mm in length ${\times}$ 2 mm in width ${\times}$ 1 mm in height) using silicone molds. After 24 hours of preparation, DC measurement was performed using Fourier transform infrared spectrometry. The same specimens were used for the evaluation of mechanical properties (flexural strength, FS; elastic modulus, E) by a three-point bending test. Data were assessed for normality, after which two-way analysis of variance (ANOVA) and post hoc Tukey's test were performed. Results: No properties of the Variolink cement were influenced by any of the considered experimental conditions. In the case of the RelyX ARC cement, DC was higher when polywave LCU was used; FS and E were not influenced by the conditions evaluated. The LuxaCore cement showed greater sensitivity to the different protocols. Conclusions: On the basis of these results, both the spectrum of light emitted and the radiant exposure used could affect the properties of resin cements. However, the influence was material-dependent.

Trichogin GA IV: an antibacterial and protease-resistant peptide

De Zotti, Marta,Biondi, Barbara,Formaggio, Fernando,Toniolo, Claudio,Stella, Lorenzo,Park, Yoonkyung,Hahm, Kyung-Soo John Wiley Sons, Ltd. 2009 Journal of Peptide Science Vol.15 No.9

<P>The antibacterial and hemolytic activities of the amphiphilic helical, membrane-active, lipopeptaibol trichogin GA IV and its [Leu<SUP>11</SUP>-OMe] analogue were compared to those of the partially helical or non-helical 8-meric or 4-meric, C-terminal short sequences, respectively. The study on trichogin GA IV was extended to several methicillin-resistant Staphylococcus aureus strains. Using a large set of enzymes, we also evaluated the resistance to proteolysis of all of the four peptides. Copyright © 2009 European Peptide Society and John Wiley & Sons, Ltd.</P>

Effects of radiant exposure and wavelength spectrum of light-curing units on chemical and physical properties of resin cements

Adriano Fonseca Lima,Stephanie Ellen Ferreira Formaggio,Ligia Franca Aires Zambelli,Alan Rodrigo Muniz Palialol,Giselle Maria Marchi,Cintia Helena Coury Saraceni,Marcelo Tavares de Oliveira 대한치과보존학회 2016 Restorative Dentistry & Endodontics Vol.41 No.4

Objectives: In this study, we evaluated the influence of different radiant exposures provided by single-peak and polywave light-curing units (LCUs) on the degree of conversion (DC) and the mechanical properties of resin cements. Materials and Methods: Six experimental groups were established for each cement (RelyX ARC, 3M ESPE; LuxaCore Dual, Ivoclar Vivadent; Variolink, DMG), according to the different radiant exposures (5, 10, and 20 J/cm2) and two LCUs (single-peak and polywave). The specimens were made (7 mm in length × 2 mm in width × 1 mm in height) using silicone molds. After 24 hours of preparation, DC measurement was performed using Fourier transform infrared spectrometry. The same specimens were used for the evaluation of mechanical properties (flexural strength, FS; elastic modulus, E) by a three-point bending test. Data were assessed for normality, after which twoway analysis of variance (ANOVA) and post hoc Tukey’s test were performed. Results: No properties of the Variolink cement were influenced by any of the considered experimental conditions. In the case of the RelyX ARC cement, DC was higher when polywave LCU was used; FS and E were not influenced by the conditions evaluated. The LuxaCore cement showed greater sensitivity to the different protocols. Conclusions: On the basis of these results, both the spectrum of light emitted and the radiant exposure used could affect the properties of resin cements. However, the influence was materialdependent.

Trichogin GA IV: A versatile template for the synthesis of novel peptaibiotics

Zotti, Marta De,Biondi, Barbara,Peggion, Cristina,Formaggio, Fernando,Park, Yoonkyung,Hahm, Kyung-Soo,Toniolo, Claudio The Royal Society of Chemistry 2012 Organic & biomolecular chemistry Vol.10 No.6

<P>Trichogin GA IV, isolated from the fungus <I>Trichoderma longibrachiatum</I>, is the prototype of lipopeptaibols, the sub-class of short-length peptaibiotics exhibiting membrane-modifying properties. This peptaibol is predominantly folded in a mixed 3<SUB>10</SUB>-/α- helical conformation with a clear, albeit modest, amphiphilic character, which is likely to be responsible for its capability to perturb bacterial membranes and to induce cell death. In previous papers, we reported on the interesting biological properties of trichogin GA IV, namely its good activity against Gram positive bacteria, in particular methicillin-resistant <I>S. aureus</I> strains, its stability towards proteolytic degradation, and its low hemolytic activity. Aiming at broadening the antimicrobial activity spectrum by increasing the peptide helical amphiphilicity, in this work we synthesized, by solution and solid-phase methodologies, purified and fully characterized a set of trichogin GA IV analogs in which the four Gly residues at positions 2, 5, 6, 9, lying in the poorly hydrophilic face of the helical structure, are substituted by one (position 2, 5, 6 or 9), two (positions 5 and 6), three (positions 2, 5, and 9), and four (positions 2, 5, 6, and 9) Lys residues. The conformational preferences of the Lys-containing analogs were assessed by FT-IR absorption, CD and 2D-NMR techniques in aqueous, organic, and membrane-mimetic environments. Interestingly, it turns out that the presence of charged residues induces a transition of the helical conformation adopted by the peptaibols (from 3<SUB>10</SUB>- to α-helix) as a function of pH in a reversible process. The role played in the analogs by the markedly increased amphiphilicity was further tested by fluorescence leakage experiments in model membranes, protease resistance, antibacterial and antifungal activities, cytotoxicity, and hemolysis. Taken together, our biological results provide evidence that some of the least substituted among these analogs are good candidates for the development of new membrane-active antimicrobial agents.</P> <P>Graphic Abstract</P><P>One or more Gly-to-Lys replacements on the hydrophilic face of the peptide-template trichogin GA IV modulate its biological properties and promote a pH-mediated, reversible, 3<SUB>10</SUB>- to α-helix transition. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1ob06178j'> </P>

The Lipid Dependence of Antimicrobial Peptide Activity Is an Unreliable Experimental Test for Different Pore Models

Bobone, Sara,Roversi, Daniela,Giordano, Lorenzo,De Zotti, Marta,Formaggio, Fernando,Toniolo, Claudio,Park, Yoonkyung,Stella, Lorenzo American Chemical Society 2012 Biochemistry Vol.51 No.51

<P>Antimicrobial peptides usually kill bacteria by making their membranes permeable. Two main models (barrel-stave and Shai–Matsuzaki–Huang) have been proposed to describe the peptide-induced pores. Although several experimental tests can be exploited to discriminate between these two models, the dependence of peptide activity on lipid properties (intrinsic curvature and membrane thickness) is routinely used for this purpose. Here, we show that, contrary to what is currently accepted, this criterion is unreliable.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/bichaw/2012/bichaw.2012.51.issue-51/bi3015086/production/images/medium/bi-2012-015086_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/bi3015086'>ACS Electronic Supporting Info</A></P>

Different mechanisms of action of antimicrobial peptides: insights from fluorescence spectroscopy experiments and molecular dynamics simulations

Bocchinfuso, Gianfranco,Palleschi, Antonio,Orioni, Barbara,Grande, Giacinto,Formaggio, Fernando,Toniolo, Claudio,Park, Yoonkyung,Hahm, Kyung-Soo,Stella, Lorenzo John Wiley Sons, Ltd. 2009 Journal of peptide science Vol.15 No.9

<P>Most antimicrobial peptides exert their activity by interacting with bacterial membranes, thus perturbing their permeability. They are investigated as a possible solution to the insurgence of bacteria resistant to the presently available antibiotic drugs. However, several different models have been proposed for their mechanism of membrane perturbation, and the molecular details of this process are still debated. Here, we compare fluorescence spectroscopy experiments and molecular dynamics (MD) simulations regarding the association with lipid bilayers and lipid perturbation for two different amphiphilic helical antimicrobial peptides, PMAP-23 and trichogin GA IV. PMAP-23, a cationic peptide member of the cathelicidin family, is considered to induce membrane permeability according to the Shai-Matsuzaki-Huang “carpet” model, while trichogin GA IV is a neutral peptide, member of the peptaibol family. Although several lines of evidence suggest a “barrel-stave” mechanism of pore formation for the latter peptide, its length is only half the normal thickness of a lipid bilayer. Both fluorescence spectroscopy experiments and MD simulations indicated that PMAP-23 associates with membranes close to their surface and parallel to it, and in this arrangement it causes a severe perturbation to the bilayer, both regarding its surface tension and lipid order. By contrast, trichogin GA IV can undergo a transition from a surface-bound state to a transmembrane orientation. In the first arrangement, it does not cause any strong membrane perturbation, while in the second orientation it might be able to span the bilayer from one side to the other, despite its relatively short length, by causing a significant thinning of the membrane. Copyright © 2009 European Peptide Society and John Wiley & Sons, Ltd.</P>